Conservatory air conditioning
By Airva Editorial Team · Checked against published UK guidance · Updated
A conservatory is the hardest room in a British house to condition, and the reason is arithmetic rather than equipment. It is a room made almost entirely of glass, with very little insulation and almost no thermal mass, attached to a house that has plenty of both. In July it collects heat far faster than any sensibly sized unit can remove it. In January it loses heat just as quickly.
Air conditioning can absolutely make a conservatory usable. But in this one room, what you do to the glazing determines whether the system succeeds — and installers who skip that conversation are selling you a unit that will run flat out and still disappoint.
Why the glass wins
Every other room in your house has walls that resist heat flow. A conservatory does not. Its roof and walls transmit solar energy almost directly into the space, and a polycarbonate or single-glazed roof is the worst offender because it faces the sky for the whole day.
Three consequences follow:
- The cooling load is enormous for the floor area. A conservatory can need several times the capacity of an internal room of the same size. Sizing it from floor area alone — which is how too many quotes are produced — will undersize it badly.
- The load peaks with the sun, not with occupancy. A south or west-facing conservatory is at its worst mid-afternoon to early evening, which is exactly when you want to sit in it.
- The heat comes back the moment the system stops. With little thermal mass, the room has almost no ability to coast.
Do the fabric work first — it is usually cheaper
This is the honest advice, and it will save you money before it costs us a lead.
A solid or insulated roof is the transformative change. Replacing a polycarbonate or glass conservatory roof with an insulated one removes the largest single heat path in both directions, and turns the space into something closer to a proper room. It costs more than air conditioning, but it fixes the problem rather than fighting it, and it makes the room usable in winter too.
Solar-control glazing or applied film on the roof and the sunniest elevations cuts transmitted solar energy substantially for a fraction of the cost of re-roofing.
External shading — awnings, blinds outside the glass, or planting — beats internal blinds decisively, because it stops the energy before it enters. Internal blinds absorb heat that is already in the room and re-radiate it.
Ventilation. Roof vents and openable panels let the hottest air escape. Many conservatories have vents that have not been opened in years.
Do these first, then size the cooling for what is left. Our house too hot in summer guide sets out the same triage for the rest of the house.
Sizing, and the honest limit
After the fabric work, air conditioning in a conservatory works well. Before it, expect a system that runs continuously on the hottest afternoons and still does not reach the set point — because it cannot, physically, remove heat as fast as the glass admits it.
A proper survey for a conservatory accounts for:
- Roof type and glazing specification, including any solar-control coating.
- Orientation and total glazed area by elevation.
- Whether the conservatory is open to the house or separated by doors. An open one is not a room, it is an extension of the house's load — and cooling it means partially cooling everything it connects to.
- Floor construction, since a solid floor gives a little useful thermal mass.
- Realistic use, because sizing for continuous 21°C on the hottest day of the decade is a different and much larger system than one sized to make the room comfortable most of the summer.
That last point is worth discussing openly with your installer. A slightly more modest target can be the difference between a sensible system and an oversized one.
Which system suits
| Option | Suitability | Notes |
|---|---|---|
| Wall-mounted split | Usually the best answer | Needs a solid wall section — often the house wall the conservatory abuts |
| Floor-mounted unit | Good where wall space is glazed | Useful when there is genuinely nowhere high to mount |
| Multi-split shared with the house | Good | Sensible if you are cooling other rooms too, but note all rooms share one mode |
| Portable | Stopgap only | The hose requires an open door or window, which in a conservatory is self-defeating |
| Evaporative cooler | Not suitable | Adds moisture; ineffective in humid UK conditions |
The mounting position is often the practical constraint: a conservatory may have only one solid wall, and it is usually the one shared with the house. Check there is a route for pipework and condensate from there before assuming it works.
The winter half is the underrated part
Most conservatory owners talk about summer, but a conservatory is unusable in January for the opposite reason. A reversible system heats the space efficiently — several units of heat per unit of electricity, against one for one from a plug-in heater [3]. For a room with no radiator, or a radiator that never keeps up, that is the difference between a room you use for four months a year and one you use for twelve.
See heating and cooling, and note that specifying a reversible system also keeps you inside permitted development, which excludes units used solely for cooling [1].
Cost, and running cost
Installation is broadly in line with any single-room job — £1,500–£3,500 for a wall-mounted split — with the caveat that a conservatory often needs a larger unit than its floor area suggests, which pushes the equipment cost up. See the cost guide.
Running cost is where a conservatory genuinely differs. A high-load room runs its system for longer, so it costs more to operate than the same unit in a bedroom. This is precisely why the fabric work pays twice: it reduces both the capacity you need to buy and the hours it runs. Our running costs guide works the arithmetic from the current unit rate of 26.32p per kWh [2].
Planning
The conservatory itself is not the planning question — the outdoor unit is. For a house in England, a reversible unit within 1.5 m³ meeting the Class G conditions is normally permitted development [1]. Conservation areas restrict elevations fronting a highway, and listed buildings have no permitted development rights at all. Our planning permission guide covers it.
Frequently asked questions
Can you air condition a conservatory? Yes, and it works well once the fabric is reasonable. Cooling a single-glazed or polycarbonate-roofed conservatory without addressing the roof will disappoint on the hottest days, because heat enters faster than a sensible unit can remove it.
Why is my conservatory so hot? Because it is mostly glass, with little insulation and almost no thermal mass. Solar energy passes almost directly into the room, and there is nothing to absorb or resist it.
What is the cheapest way to cool a conservatory? External shading and roof ventilation, then solar-control film. These reduce the problem rather than fighting it, and they cost far less than equipment.
Do I need a bigger unit than for a normal room? Usually yes — often substantially. Sizing must come from a calculation that accounts for the glazing, not from floor area.
Is a portable unit any good in a conservatory? Poorly. The exhaust hose needs an opening, and an open door or window in a conservatory undoes the cooling faster than almost anywhere else in the house.
Will it heat the conservatory in winter? Yes, and this is often the bigger benefit. A reversible unit heats efficiently and turns a seasonal room into a year-round one.
Get it sized against the glazing
Tell us about the conservatory — roof type, orientation, glazed area and whether it is open to the house — and we will match you with one vetted installer who will calculate the load properly rather than guess from the floor plan: get an installer match.